title: The photosynthesis affected mutant68-like protein evolved from a PSII assembly factor to mediate assembly of the chloroplast NAD(P)H dehydrogenase complex in Arabidopsis.
abstract: In vascular plants, the chloroplast NAD(P)H dehydrogenase complex (NDH-C) is assembled from five distinct subcomplexes, the membrane-spanning (subM) and the luminal (subL) subcomplexes, as well as subA, subB, and subE. The assembly process itself is poorly understood. Vascular plant genomes code for two related intrinsic thylakoid proteins, photosynthesis-affected mutant68 (PAM68), a photosystem II assembly factor, and photosynthesis-affected mutant68-like (PAM68L). As we show here, inactivation of Arabidopsis thaliana PAM68L in the pam68l-1 mutant identifies PAM68L as an NDH-C assembly factor. The mutant lacks functional NDH holocomplexes and accumulates three distinct NDH-C assembly intermediates (subB, subM, and subA+L), which are also found in mutants defective in subB assembly (ndf5) or subM expression (chlororespiratory reduction4-3 mutant). NDH-C assembly in the cyanobacterium Synechocystis sp PCC 6803 and the moss Physcomitrella patens does not require PAM68 proteins, as demonstrated by the analysis of knockout lines for the single-copy PAM68 genes in these species. We conclude that PAM68L mediates the attachment of subB- and subM-containing intermediates to a complex that contains subA and subL. The evolutionary appearance of subL and PAM68L during the transition from mosses like P. patens to flowering plants suggests that the associated increase in the complexity of the NDH-C might have been facilitated by the recruitment of evolutionarily novel assembly factors like PAM68L.
authors.affiliation: Plant Molecular Biology (Botany), Department Biology I, Ludwig-Maximilians-Universität, 82152 Martinsried, Germany.
authors.forename: Ute
authors.initials: U
authors.lastname: Armbruster
authors.forename: Thilo
authors.initials: T
authors.lastname: Rühle
authors.forename: Renate
authors.initials: R
authors.lastname: Kreller
authors.forename: Christoph
authors.initials: C
authors.lastname: Strotbek
authors.forename: Jessica
authors.initials: J
authors.lastname: Zühlke
authors.forename: Luca
authors.initials: L
authors.lastname: Tadini
authors.forename: Thomas
authors.initials: T
authors.lastname: Blunder
authors.forename: Alexander P
authors.initials: AP
authors.lastname: Hertle
authors.forename: Yafei
authors.initials: Y
authors.lastname: Qi
authors.forename: Birgit
authors.initials: B
authors.lastname: Rengstl
authors.forename: Jörg
authors.initials: J
authors.lastname: Nickelsen
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Frank
authors.forename: Dario
authors.initials: D
authors.lastname: Leister
mesh_terms: D017360:Arabidopsis / Q000235:genetics* / Q000378:metabolism; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D019068:Bryopsida / Q000378:metabolism; D060365:Chloroplast Proteins / Q000235:genetics / Q000378:metabolism*; D002736:Chloroplasts / Q000201:enzymology*; D009252:NADPH Dehydrogenase / Q000235:genetics / Q000378:metabolism*; D010788:Photosynthesis; D010802:Phylogeny; D046939:Synechocystis / Q000378:metabolism
chemical_list: D029681:Arabidopsis Proteins; D060365:Chloroplast Proteins; D009252:NADPH Dehydrogenase